Electronic voltage regulator system



June 14, 1955 c. w. ARMSTRONG 2,710,940

ELECTRONIC VOLTAGE REGULATOR SYSTEM Filed Feb. 24, 1951 IN VEN TOR.

[mamas W. HRMSTRDNE M/I- M ATTORNEY Unite States Patent Ofitice 2,710,040 Patented June 14, 1955 Charles W. Armstrong,

Radio Corporation of ware Collingswood, N. J., assignor to America, a corporation of Dela- Application February 24, 1951, Serial No. 212,580 1 Claim. (Cl. 323-22) This invention relates to voltage regulators, and more particularly to electronic voltage regulator systems.

In the construction of a television transmitter, in order to obtain a desired output signal level, one or more stages of linear amplifiers must be used. To maintain good linearity in the output over the entire range of signal from white level to sync peaks, the grid bias supplied to these amplifiers must be maintained constant regardless of grid current. However, these amplifiers, which are usually class B linear power amplifiers, do have grid current which varies from zero during the lower portion of the white region to a maximum at sync peaks.

Grid current represents current that must be absorbed in the grid bias supply rather than furnished by it, in order that the grid bias voltage remain constant. In the conventional type of voltage regulator circuit there is employed a series connected current regulating tube and a bleeder resistor across the output of the supply which is also used for obtaining a control voltage. The grid current flows through this resistor thus bucking out the regulator current normally flowing therethrough. In order to maintain the voltage supplied as grid bias substantially constant, the regulator must supply to this resistor at all times a current at least equal to the maximum grid current expected to be obtained. Since the greater proportion of the signals in the television transmitter are in the white region where little or no grid current is drawn by the amplifiers, this type of voltage regulator is inefiicient for grid bias voltage regulation.

It is therefore an object of the present invention to provide an improved voltage regulator system wherein the output voltage is maintained substantially constant regardless of the direction of load current flow.

It is a further object of the present invention to provide an improved voltage regulator system for use with loads characterized by having a reverse load current flow that is more eflicient than those used heretofore.

It is a still further object of the present invention to provide a novel and improved voltage regulator system.

These and further objects of the present invention are achieved by providing a voltage regulator system including a substantially regulated source of potential, a control electron discharge tube having a plate load resistor and means for maintaining its cathode potential constant, such as a gaseous regulator tube connected to its cathode. The regulated potential from the source is applied to the tube through the plate load resistor and the gaseous regulator tube. A pair of output terminals are also provided across which a load electron discharge tube is connected. The end of the plate load resistor to which the regulated voltage is applied is connected to the output terminal to which the load tube anode is connected. A control resistor connects the end of the gaseous regulator tube to which the regulated potential is applied to the other output terminal. The anode of the control tube is connected to the grid of the load tube. The control tube grid is connected to the control resistor to derive a control potential therefrom. Any reverse current from the load applied to the output terminals causes the control voltage derived from the control resistor to be more negative, thus reducing the current conducted by the control tube which in turn causes the load tube to become more conductive. This shunts the reverse current through the load tube permitting the voltage applied to the load across the output terminals to be maintained substantially constant.

The novel features of the present invention as well as the invention itself, both as to its organization and method of operation will best be understood from the following description when read in connection with the accompanying drawing, which is a circuit diagram of an embodiment of the present invention.

Referring now to the drawing, a source of substantially regulated direct current is supplied by a power transformer 10 having its primary 12 connected to an alternating current source and its center tapped secondary winding 14 connected to a double diode rectifier tube 16 in a manner well known to the art. The center tap of the secondary winding is connected to a power choke coil 18. A filter condenser 20 is connected from each end of the choke coil 18 to a lead 22 from the cathode of the power rectifier tube 16. A voltage dropping resistor 24 is connected in series with the power choke coil and a pair of gaseous voltage regulator tubes 26 are connected in series between an end of the voltage dropping resistor 24 and the lead 22 from the rectifier tube cathode. It will be noted that the source of substantially regulated potential described thus far is a conventional one. Any other system for obtaining a source of regulated potential may be used in its place.

An electron discharge tube 30 preferably of the pentode variety serves as a control tube and has a load resistor 38 connected from its anode 32 to the lead 22 from the rectifier tube cathode. Another gaseous voltage regulator tube is connected between the cathode 36 of the control tube and the output end of the voltage dropping resistor 24. The regulator tube 40 serves to maintain the control tube cathode potential substantially constant. Bias for the screen grid and cathode of the control tube is provided by the seriesed voltage dropping resistors 42, 44 connected between the rectifier cathode lead 22, the control tube screen grid and cathode 36. The control tube suppressor grid is connected to its cathode.

A second voltage dropping resistor 46 which serves as a control voltage supplying resistor serves to connect the gaseous regulator tube 40 for the cathode of the control tube to one of a pair of output terminals 48. Since this control resistor 46 must carry the load current it consequently must have a large power carrying capacity. Although the resistor 46 can be made variable, in order to obtain fine steps in control voltage it is paralleled for economic reasons by a voltage divider including two high value resistors 50, 52 in series with a potentiometer 54. The arm of the potentiometer 54 is connected to the control tube control grid 34. The rectifier tube cathode lead 22 is connected to the other of the pair of output terminals 48 which, in view of the utilization of this voltage rectifier for grid bias purposes, is also connected to ground.

A load electron discharge tube is connected across the output terminals 48 with its anode 62 connected to the grounded output terminal and its cathode 66 connected to the other or negative output terminal. The load tube grid 64 is connected to the anode 32 of the control tube 30.

The grid circuit to be biased is connected to the output terminals 48. Only a small amount of current is drawn from the regulated potential source in order to establish the operating point of the control and load tubes. Any grid current or reverse current from the load is made to flow through the load tube which is normally drawing only a very'small' current. As many tubes as are required current starts to flow the negativeoutput terminal 48' goes more negative. This causes the voltage drop across the control resistor 46, which is in the negative leg of the regulated power supply, to change. This also serves to make the potential point at which the control tube grid 34' is connected to the. potentiometer 54 across the control resistor 46 to go more negative. Consequently the control tube plate current is decreased and the potential applied to the load tube grid 64 is. more positive. This permits the load tube to conduct the reverse grid current thus reducing the voltage across the output terminals and the load to a value only infinitesimally larger than before any reverse current was flowing. reverse current falls off the potential obtained from the control resistor 46 begins to get more positive and a more negative signal is applied to the grid of the load tube thus reducingv its conductivity. The output voltage obtainable is adjustable with adjustments in the control voltage applied to the control tube grid.

In order to illustrate an operative embodiment of the invention which was built, and not to serve as a limitation, the gaseous regulator tube 40 connected to thecontrol tube cathode was a VR75, the control tube 30 ;7;

was a 651-17 and two- 6AS7G load tubes 60 were used. The power supply furnished approximately 300 volts. The output voltage available at the output terminals was variable from 85 to 130 volts. Excellent regulation was obtainable with grid currents which varied from. zero to 400 milliamperes. The current. supplied to the regulator tubes was only a small fraction of the current that the bias supply could absorb and therefore the system was AS the very eflicient when compared with systems used heretofore.

From the foregoing description, it will be readily apparent that an improved, efficient and novel voltage regulation system is provided for loads of the type that may provide reverse current flow.

What is claimed is:

A voltage supply system comprising a rectifier-type power supply having a pair of output terminals, at least one gaseous voltage regulator device connected directly between said output terminals to regulate the voltage therebetween, an electron discharge device having at least anode, cathode and controlelectrodes, a gaseous voltage regulator device having two electrodes, a resistor connected between one of said terminals and said anode, means coupling said cathode directly to one electrode of said last-named regulator device, means coupling the other electrode of said lastanamed regulator device directly to the other of said terminals, an electron flowcontrol device having: at least anode, cathode and control electrodes, means coupling said last-named anode directly to said one terminal, means coupling said last-named control electrode directly to'the common junction of said resistor and said first-named anode, a resistor connected betweensaid' last-named cathode and said other terminal, and a connection between said last-named resistor and said first-named control electrode.

References Cited in the file of this patent UNITED- STATES PATENTS 2,372,432 Keizer Mar. 27, 1945 2,434,939 Levy Jan. 27, 1948 2,475,613 Hastings July 12, 1949 2,499,443 Young Mar. 7, 1950' FOREIGN PATENTS 237,479 Switzerland of 1945 326,837 Italy June 22, 1935 

